This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A064819 #28 Nov 06 2024 10:19:54
%S A064819 -7,-19,-19,89,2141,29741,510149,9699161,223092029,6469692269,
%T A064819 200560488761,7420738133129,304250263525361,13082761331667821,
%U A064819 614889782588488601,32589158477190041249,1922760350154212635349,117288381359406970978781
%N A064819 a(n) = p(1)*p(2)*...*p(n) - p(n+1)^2, where p(i) = i-th prime.
%C A064819 It is known that a(n) > 0 for n >= 4.
%D A064819 R. Honsberger, Mathematical Diamonds, MAA, 2003, see p. 79. [Added by _N. J. A. Sloane_, Jul 05 2009]
%D A064819 H. Rademacher & O. Toeplitz, The Enjoyment of Mathematics, pp. 187-192 Dover NY 1990.
%D A064819 J. V. Uspensky and M. A. Heaslet, Elementary Number Theory, McGraw-Hill, NY, 1939.
%H A064819 Harry J. Smith, <a href="/A064819/b064819.txt">Table of n, a(n) for n = 1..100</a>
%H A064819 S. Bulman-Fleming and E. T. H. Wang, <a href="http://www.jstor.org/stable/2686778">Problem 356</a>, College Math. J., 20 (1989), 265.
%H A064819 Wikipedia, <a href="https://en.wikipedia.org/wiki/Bonse%27s_inequality">Bonse's inequality</a>
%t A064819 FoldList[Times, Most[#]] - Rest[#]^2 & [Prime[Range[25]]] (* _Paolo Xausa_, Nov 06 2024 *)
%o A064819 (PARI) { p=1; for (n=1, 100, p*=prime(n); write("b064819.txt", n, " ", p - prime(n + 1)^2) ) } \\ _Harry J. Smith_, Sep 27 2009
%o A064819 (PARI) a(n) = prod(k=1, n, prime(k)) - prime(n+1)^2; \\ _Michel Marcus_, Jun 19 2018
%o A064819 (Python)
%o A064819 from sympy import prime, primorial
%o A064819 def A064819(n): return primorial(n)-prime(n+1)**2 # _Chai Wah Wu_, Feb 24 2023
%Y A064819 Cf. A135734, A060882, A062234.
%K A064819 sign
%O A064819 1,1
%A A064819 _N. J. A. Sloane_, Oct 23 2001